Memory protection unit, memory protection method, and computer-readable record medium in which memory protection program is recorded

Abstract

A memory protection unit, a memory protection method and a computer-readable record medium in which a memory protection program is recorded is provided which are capable of preventing a memory from being improperly rewritten by a malfunction in a subroutine. This memory protection unit includes: a memory which has at least one memory area that is used by at least one subroutine, and in which a writing attribute that shows a writing permission or a writing prohibition can be set for every memory area; a subroutine choice section which chooses a subroutine that executes a processing request; a memory-area specification section which specifies a memory area that is used by the subroutine; and a subroutine calling section which sets, to the writing permission, the writing attribute of the specified memory area, calls the chosen subroutine, and sets, to the writing prohibition, the writing attribute of the memory area after completing the execution of the subroutine.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to memory management in an operating system. Specifically, it relates to a memory protection unit which protects a memory from its improper rewriting. In addition, it also relates to a memory protection method and a computer-readable record medium in which a memory protection program is recorded, which are used to do the same. [0003] 2. Description of the Related Art [0004] Conventionally, the following method is known as the art of managing a memory in an operating system, particularly protecting a memory. An application which operates in such a system is divided into several processes. Then, a virtual address space is allocated for each process. [0005] Such a process includes one address space, and is a processing unit which reads and writes in a memory area within the address space. Each process corresponds to a single address space. A thread is a processing unit which shares one add...

AI Technical Summary

Benefits of technology

[0014] In order to resolve the above described conventional disadvantages, it is an object of the present invention to provide a memory protection unit, a memory protection method and a computer-readable record medium in which memory protection program is recorded which are capable of preventing a memory from being improperly rewritten by a malfunction in a subroutine.

Problems solved by technology

Hence, a process in operation within the allocated virtual address space cannot obtain access to a memory area in the virtual address space of another process.

Thereby, even though something is wrong with software, it can only affect the area within a process unit.

This may lower the whole system's performance.

Such a deterioration in the performance can largely affect, especially, so-called embedded equipment, such as a cellular phone, a digital television and a household electrical appliance.

Thus, in an operating system which presides over the control of embedded equipment, it is difficult to adopt the method of allocating a virtual address space for each process.

However, it has no access to the memory areas of the other domains.

However, according to the prior art, in a system which is configured by one or a small number of threads, it is almost impossible to divide a memory into smaller domain units.

However, in an environment where there are only one or a few domains, a malfunction can affect a larger area within a domain.

This makes it difficult to prevent a memory from being improperly rewritten.

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